1. Field of the Invention
The invention relates to electric motors, particularly to low-voltage gearless commutator motors, and can be used as motor-wheels in vehicles such as electrically propelled bicycles, scooters, motorcycles, electric-motor cars, etc., as well as in other technologies.
2. Background of the Invention
Devices and machines provided with a reduction gear and an asynchronous electric motor are widely used in various technologies, in particular, in transportation. Asynchronous motors, being ecologically safe, reliable, and economically effective, offer a number of advantages over internal combustion engines.
The best prospects are related to a gearless (direct-drive) motor-in-wheel (motor-wheel) in which the wheel rotation is induced directly by the electromagnetic interaction between the built-in rotor and stator magnetic systems. In prior art, there is a motor-wheel comprising a rim and a shaft with built-in asynchronous electric motor. The motor represents a disk asynchronous electric machine comprising a stator with magnetic conductor, windings, and current lead, which is mounted on the immobile axis, and a rotor with short-circuit winding and magnetic conductors situated on both sides of the stator. The stator and rotor in assembly comprise a wheel capable of spinning. This motor-wheel design provides high reliability due to the absence of a mechanical reduction gear and is characterized by better cooling conditions as compared to the traditional design, which is ensured by radial channels carrying a cooling medium. However, use of the asynchronous electric motor still leads to high heat evolution and requires a complicated control system and high-voltage power supply. Such a motor-wheel offers no prospects in electric energy recuperation during motion of retardation of the vehicle.
Another built-in motor known in the prior art comprises two main parts: an immobile stator, mounted on the axis and provided with a magnetic conductor and a set of uniformly arranged permanent magnets, and a mobile rotor bearing a rim and containing at least two groups of electromagnets. A collector distributor (commutator) is mounted on the stator and provided with current-conducting plates connected to a dc current source. The rotor bears current collectors occurring in electric contact with plates of the collector distributor.
Said motor-wheel can be implemented in several modifications and variants. Advantages of such design are the absence of a reducing gear, use of low-voltage power sources, absence of supplementary electronic circuits, possibility of energy recuperation, and small size and weight. By combining the main elements of this motor-wheel with auxiliary elements, it is possible to create a variety of analogous devices retaining all advantages of said motor-wheel.
However, the above motor-wheel and its analogs still have some disadvantages, the main of these being large start and transient currents in course of starting and accelerating the vehicle. This leads to rapid degradation and a decrease in the working life of storage batteries and to unfavorable thermal regimes. Another drawback is low efficiency of recovery and use of electric energy. Finally, said electric motors are characterized by relatively low torque, which considerable reduces the field of possible practical applications. Technical solutions suggested to eliminate these disadvantages are based on the use of high-voltage power sources and complicated control schemes, which increase the cost and decrease reliability of such systems in exploitation.